1. Field of the Invention
The present invention relates to a camera for reproducing an image onto a photosensitive material sheet. The present invention also relates to a photosensitive material feed unit for use in such a camera.
2. Description of the Prior Art
The camera disclosed in Japanese Patent Laid-Open Gazette No. 1-189657 can be taken as an example of a camera for producing a printing plate, the reproduction camera being proposed also by the inventor of the present application. The camera comprises a projection optical system which illuminates an original having an image to be reproduced and which directs image light reflected from the original toward a photosensitive material. The projection optical system has a slit. Thus, image light being projected onto the photosensitive material through the projection optical system is provided in the form of a slit. In the camera, the photosensitive material and the original are synchronously fed while the slit image light is projected onto the photosensitive material. Consequently, the image of the original is reproduced on the photosensitive material. The term "scan-exposure camera" refers to this type of camera.
The scan-exposure camera is capable of changing a reproduction magnification of a reproduced image by adjusting a magnification of the projection optical system installed therein. In addition, by repeatedly reproducing an image of the same single original, the camera produces a printing plate on which a plurality of images are placed side by side. To reproduce a plurality of images on a single printing plate is referred to as "multi-placing."
In reproducing a plurality of images to produce a printing plate, there has been a large demand for a different magnification for each reproduced image. Assuming here, for example, to print two identical leaflets which are different only in size. If images of a high and a low magnification are reproduced on the same printing plate, only a single printing plate will be necessary. This saves the number of printing plates required as well as labor involved in printing.
The prior art scan-exposure camera, in spite of the demand as above, is not capable of changing a reproduction magnification for each image to be reproduced on the same and single printing plate.
Further, even if capable of changing a magnification for each image to be reproduced, the conventional scan-exposure camera is not still free from a problem as recited in the following: That is, it is extremely difficult to treat a region other than a so-called "scanning region" in which each reproduced image is included. In this specification, the term "non-scanning region" will refer to a region other than a scanning region. In general, a scan-exposure camera reproduces a plurality of images onto a negative type photosensitive material, to thereby form a printing plate. An unexposed portion of a negative photosensitive material is inked but an exposed portion thereof is not inked. A printing plate available from such a scan-exposure camera is applied to a printer without receiving any additional treatments prior to printing. Therefore, non-scanning regions must be generally exposed without fail in order to obviate inking thereto. On the other hand, when images are reproduced at different magnifications, sizes of non-scanning regions vary accordingly depending on the magnifications. Thus, it is extremely difficult to generally expose the non-scanning regions.
As a possible solution to this problem, a bottom surface of a platen cover may be white-colored. This causes illumination light to be reflected, so that the non-scanning regions of a photosensitive material are entirely exposed with the light beam reflected from the bottom surface thereof. Adopting this solution, however, would lead to an increased size of a scan-exposure camera if non-scanning regions are large.
In addition to the two problems described above, there is another problem in the conventional scan-exposure camera, that is, a problem relating to an original setting position. As well known in the art, there are two ways of mounting a printing plate to a printer, that is, top-or-bottom mounting and side mounting. A printing plate takes a holding space in which it is fixed to a plate cylinder, and the holding space must be taken differently depending on a type of the printing plate, i.e., whether the printing plate is of a top-or-bottom-mounted type or of a side-mounted type. This requires an original to be properly mounted to an original holder in conformance with a type of a printing plate. In the conventional scan-exposure camera, however, an optimum setting position of an original to be mounted to an original holder varies according to a mounting method and a reproduction magnification. This requires movement of the original in pursuit of the optimum position at every original replacement, thus highly labor consuming.